Vaso-occlusive device delivery system

ABSTRACT

A vaso-occlusive device delivery assembly includes a pusher assembly having proximal and distal ends, a conductive sacrificial link disposed at the distal end of the pusher assembly, and a vaso-occlusive device secured to the pusher assembly by the sacrificial link. The pusher assembly includes first and second conductors extending between the proximal and distal ends thereof. The sacrificial link is electrically coupled between the first and second conductors, such that the first conductor, sacrificial link and second conductor form an electrical circuit, and, when a disintegration current is applied through the sacrificial link through the first and second conductors, the sacrificial link thermally disintegrates, thereby releasing the attachment member and vaso-occlusive device from the pusher assembly.

RELATED APPLICATION DATA

The present application is a continuation of U.S. Pat. ApplicationSerial No. 16/711,327, filed Dec. 11, 2019, now U.S. Pat. No.11,622,772, which is a continuation of U.S. Pat. Application Serial No.15/664,247, filed Jul. 31, 2017, now U.S. Pat. No. 10,537,333, which isa continuation of U.S. Pat. Application Serial No. 14/206,176, filedMar. 12, 2014, now U.S. Pat. No. 9,717,502, which claims the benefitunder 35 U.S.C. § 119 to U.S. Provisional Application Serial No.61/785,730, filed Mar. 14, 2013. The foregoing applications are herebyincorporated by reference into the present application in theirentirety.

FIELD

The field of the disclosed inventions generally relates to systems anddelivery devices for implanting vaso-occlusive devices for establishingan embolus or vascular occlusion in a vessel of a human or veterinarypatient. More particularly, the disclosed inventions relate todetachment using a thermally disintegrable link.

BACKGROUND

Vaso-occlusive devices or implants are used for a wide variety ofreasons, including treatment of intra-vascular aneurysms. Commonly usedvaso-occlusive devices include soft, helically wound coils formed bywinding a platinum (or platinum alloy) wire strand about a “primary”mandrel. The coil is then wrapped around a larger, “secondary” mandrel,and heat treated to impart a secondary shape. For example, U.S. Pat. No.4,994,069, issued to Ritchart et al., which is fully incorporated hereinby reference as though set forth in full, describes a vaso-occlusivedevice that assumes a linear, helical primary shape when stretched forplacement through the lumen of a delivery catheter, and a folded,convoluted secondary shape when released from the delivery catheter anddeposited in the vasculature.

In order to deliver the vaso-occlusive devices to a desired site in thevasculature, e.g., within an aneurysmal sac, it is well-known to firstposition a small profile, delivery catheter or “micro-catheter” at thesite using a steerable guidewire. Typically, the distal end of themicro-catheter is provided, either by the attending physician or by themanufacturer, with a selected pre-shaped bend, e.g., 45°, 26°, “J”, “S”,or other bending shape, depending on the particular anatomy of thepatient, so that it will stay in a desired position for releasing one ormore vaso-occlusive device(s) into the aneurysm once the guidewire iswithdrawn. A delivery or “pusher” wire is then passed through themicro-catheter, until a vaso-occlusive device coupled to a distal end ofthe pusher assembly is extended out of the distal end opening of themicro-catheter and into the aneurysm. Once in the aneurysm, segments ofsome vaso-occlusive devices break off to allow more efficient andcomplete packing. The vaso-occlusive device is then released or“detached” from the end of the pusher assembly, and the pusher assemblyis withdrawn back through the catheter. Depending on the particularneeds of the patient, one or more additional occlusive devices may bepushed through the catheter and released at the same site.

One well-known way to release a vaso-occlusive device from the end ofthe pusher assembly is through the use of an electrolytically severablejunction, which is a small exposed section or detachment zone locatedalong a distal end portion of the pusher assembly. The detachment zoneis typically made of stainless steel and is located just proximal of thevaso-occlusive device. An electrolytically severable junction issusceptible to electrolysis and electrolytically disintegrates when thepusher assembly is electrically charged in the presence of an ionicsolution, such as blood or other bodily fluids. Thus, once thedetachment zone exits out of the catheter distal end and is exposed inthe vessel blood pool of the patient, a current applied through anelectrical contact to the conductive pusher completes an electrolyticdetachment circuit with a return electrode, and the detachment zonedisintegrates due to electrolysis.

While electrolytically severable junctions have performed well, thereremains a need for other systems and methods for deliveringvaso-occlusive devices into vessel lumens.

SUMMARY

In one embodiment of the disclosed inventions, a vaso-occlusive devicedelivery assembly includes a pusher assembly having proximal and distalends, a conductive sacrificial link disposed at the distal end of thepusher assembly, and a vaso-occlusive device secured to the pusherassembly by the sacrificial link. The pusher assembly includes first andsecond conductors extending between the proximal and distal endsthereof. The sacrificial link is electrically coupled between the firstand second conductors, such that the first conductor, sacrificial linkand second conductor form an electrical circuit, and, when adisintegration current is applied through the sacrificial link throughthe first and second conductors, the sacrificial link thermallydisintegrates, thereby releasing the attachment member andvaso-occlusive device from the pusher assembly.

In some embodiments, the vaso-occlusive device delivery assembly alsoincludes an attachment member secured to the vaso-occlusive device andsecured to the pusher assembly by the sacrificial link. The attachmentmember may include a meltable tether, such that, when a heating current,less than the disintegration current, is applied through the sacrificiallink through the first and second conductors, the sacrificial link isheated by resistive heating to a temperature sufficient to sever themeltable tether without disintegrating the sacrificial link, therebydetaching the vaso-occlusive device from the pusher assembly.

In some embodiments, the vaso-occlusive device delivery assemblyincludes a power supply electrically connected to the first and secondconductors, where the power supply is controllable to selectivelydeliver the disintegration current or the heating current through thesacrificial link. The vaso-occlusive device delivery assembly may alsoinclude a third conductor extending between the proximal and distal endsof the pusher assembly and electrically connected to the sacrificiallink, such that the third conductor, sacrificial link, and secondconductor form an electrical circuit, where the third conductor has agreater resistivity than the first conductor, such that, when thedisintegration current is applied through the sacrificial link throughthe third and second conductors, the sacrificial link is heated byresistive heating to a temperature sufficient to melt the tether withoutdisintegrating the sacrificial link.

In some embodiments, the pusher assembly also includes first and secondload bearing connectors that electrically and mechanically connect thesacrificial link to the respective first and second conductors. Thesacrificial link and the load bearing conductor may be mechanically tiedto each other. The pusher assembly may also include a cylindrical bodydisposed around and thermally insulating the sacrificial link, where thecylindrical body defines a cavity in which the sacrificial link islocated.

In some embodiments, the sacrificial link includes an electricallyconductive polymer tube defining an axial lumen, where a distal end ofthe first conductor is disposed within the axial lumen. The electricallyconductive polymer tube may have a radially enlarged distal portion, anda proximal end of the vaso-occlusive device may be secured to thepolymer tube by an interference fit with the radially enlarged distalportion. In other embodiments, the proximal end of the vaso-occlusivedevice may be secured to the polymer tube by an adhesive, a weld, ormechanical bonding.

In other embodiments, the sacrificial link includes an elongate linkmember defining a longitudinal bore therein and a proximal end openingin communication with the longitudinal bore, where the bore has a closeddistal end, and where a distal end of the first conductor extends intothe longitudinal bore. In some of those embodiments, the distal end ofthe first conductor includes a protrusion extending obliquely to alongitudinal axis of the first conductor and configured to strengthen amechanical connection between the first conductor and the sacrificiallink. In some others of those embodiments, the distal end of the firstconductor includes a radially enlarged portion configured to concentratecurrent density and to strengthen a mechanical connection between thefirst conductor and the sacrificial link.

In some embodiments, the pusher assembly defines a lumen, and the firstand second conductors extend between the proximal and distal ends of thepusher assembly in the lumen. In other embodiments, the second conductoris a conductive tubular pusher conduit extending between the proximaland distal ends of the pusher assembly, and the first conductor extendsbetween the proximal and distal ends of the pusher assembly through thepusher conduit.

In another embodiment of the disclosed inventions, a vaso-occlusivedevice is attached to a pusher assembly secured thereto by a connectionformed between a sacrificial link coupled to a distal end of the pusherassembly and a tether secured to the vaso-occlusive device. In thatembodiment, a method of detaching the vaso-occlusive device from thepusher assembly includes applying a first current through thesacrificial link to heat the sacrificial link by resistive heating to afirst temperature sufficient to melt the tether without disintegratingthe sacrificial link, and applying a second current, greater than thefirst current, to the sacrificial link to heat the sacrificial link byresistive heating to a second temperature higher than the firsttemperature, thereby thermally disintegrating the sacrificial link.

In yet another embodiment of the disclosed inventions a vaso-occlusivedevice delivery assembly includes a pusher assembly having proximal anddistal ends, and first and second conductors extending between theproximal and distal ends of the pusher assembly. The vaso-occlusivedevice delivery assembly also includes a sacrificial link disposed atthe distal end of the pusher assembly and electrically connected to thefirst and second conductors, and a vaso-occlusive device secured to thepusher assembly by the sacrificial link. The sacrificial link includesan electrically conductive member and an electrically insulative member.An insulated portion of the electrically conductive member is disposedin the electrically insulative member, leaving an exposed portion of theelectrically conductive member. The vaso-occlusive device is secured tothe exposed portion, such that, when a current is applied through thesacrificial link through the first and second conductors, thesacrificial link is heated by resistive heating, causing the exposedportion of the electrically conductive member to thermally disintegrate,thereby detaching the vaso-occlusive device from the pusher assembly.

In some embodiments, the vaso-occlusive member includes astretch-resisting member having a distal end secured to a distal portionof the vaso-occlusive member and a proximal end secured to an adapterdisposed in a lumen of the vaso-occlusive member at a proximal end ofthe vaso-occlusive member, where the adapter is secured to theelectrically conductive portion of the sacrificial link. In thoseembodiments, the adapter may include a flattened body defining anopening at a distal end thereof, and where the stretch-resisting memberforms a loop passing through the opening.

In some embodiments, the vaso-occlusive device is secured to adetachment location on the sacrificial link, where the exposed portionof the electrically conductive member has a cross-sectional area thatdecreases along a length of the exposed portion to a minimumcross-sectional area proximate the detachment location. Alternatively oradditionally, the electrically insulative member may define an opening,where the exposed portion of the electrically conductive member spansthrough the opening, and the vaso-occlusive device may be secured to theelectrically conductive member within the opening.

In various embodiments, the electrically insulative member may beover-molded onto or co-molded with the electrically conductive member.

In still another embodiment of the disclosed inventions, avaso-occlusive device delivery assembly includes a pusher assemblydefining a lumen, a vaso-occlusive device defining a vaso-occlusivedevice lumen, and releasably attached to the pusher assembly by aconnector member. The pusher assembly defines proximal and distal ends,with the pusher lumen extending therebetween. The pusher assembly alsoincludes first and second conductors extending between its proximal anddistal ends. The connector member includes a proximal tubular memberdisposed in the pusher lumen and attached to the pusher assembly, adistal tubular member disposed in the vaso-occlusive device lumen andattached to the vaso-occlusive device, and a sacrificial memberelectrically connected to the first and second conductors. Thesacrificial member includes a proximal portion extending through theproximal connector member, a distal portion extending through the distalconnector member, and an exposed middle portion disposed between theproximal and distal connector members, such that, when a current isapplied through the sacrificial member through the first and secondconductors, the sacrificial member is heated by resistive heating,causing the middle portion of the sacrificial member to thermallydisintegrate, thereby detaching the vaso-occlusive device from thepusher assembly. The vaso-occlusive device may include astretch-resisting member having a distal end secured to a distal portionof the vaso-occlusive device, where a distal end connector portion ofthe sacrificial member extends distally of the distal connector member,and is secured to a proximal end of the stretch-resisting member.

In yet another embodiment of the disclosed inventions, a vaso-occlusivedevice delivery assembly includes a pusher assembly defining proximaland distal ends, with first and second conductors extending between theproximal and distal ends; and a vaso-occlusive device releasablyattached to the pusher assembly by a connector member. The connectormember includes a proximal connecting member secured to the pusherassembly, a distal connecting member secured to the vaso-occlusivedevice, and a sacrificial member electrically connected to the first andsecond conductors. The sacrificial member includes a proximal portionsecured within the proximal connecting member, and a distal portionextending distally of the proximal connecting member and secured to thedistal connecting member, to thereby attach the pusher assembly to thevaso-occlusive device, such that, when a current is applied through thesacrificial member through the first and second conductors, thesacrificial member is heated by resistive heating, causing the middleportion of the sacrificial member to thermally disintegrate, therebydetaching the vaso-occlusive device from the pusher assembly.

In some embodiments, the proximal and distal connectors each have aflattened profile. The pusher assembly may also include a distal endcoil having open pitch windings, and the proximal connector member maydefine a plurality of fingers that are interlaced between adjacent openpitched windings of the pusher assembly distal end coil. Thevaso-occlusive member may include a vaso-occlusive coil having openpitch windings at a proximal end thereof, and the distal connectormember may define a plurality of fingers that are interlaced betweenadjacent open pitched windings at the proximal end of the vaso-occlusivecoil.

In any of the above embodiments, the sacrificial link may includetitanium, titanium alloy, magnesium, magnesium alloy, or an electricallyconductive polymer. The electrically conductive polymer may be selectedfrom the group consisting of polyacetylene, polypyrrole, polyaniline,poly(p-phenylene vinylene), poly(thiophene),poly(3,4-ethylenedioxythiophene), and poly(p-phenylene sulfide). Theelectrically conductive polymer may also be a powder-filled orfiber-filled composite polymer.

Other and further aspects and features of embodiments of the disclosedinventions will become apparent from the ensuing detailed description inview of the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of embodiments of thedisclosed inventions, in which similar elements are referred to bycommon reference numerals. These drawings are not necessarily drawn toscale. In order to better appreciate how the above-recited and otheradvantages and objects are obtained, a more particular description ofthe embodiments will be rendered, which are illustrated in theaccompanying drawings. These drawings depict only typical embodiments ofthe disclosed inventions and are not therefore to be considered limitingof its scope.

FIG. 1 is a schematic view of a vaso-occlusive device delivery system,according to one embodiment of the disclosed inventions.

FIG. 2 is a side view of an occlusive coil in a natural state mode,illustrating one exemplary secondary configuration according to anembodiment of the disclosed inventions.

FIGS. 3-18, 24 and 25 are detailed longitudinal cross-sectional views ofvaso-occlusive device delivery systems according to various embodimentsof the disclosed inventions, which depict the junction between thevarious pusher assemblies and vaso-occlusive devices.

FIGS. 19 and 23 are side views of sacrificial links according to variousembodiments of the disclosed inventions.

FIGS. 20-22 are perspective views of sacrificial links according tovarious embodiments of the disclosed inventions.

FIGS. 26-28 are detailed schematic views of vaso-occlusive devicedelivery systems according to various embodiments of the disclosedinventions, which depict the junction between the various pusherassemblies and vaso-occlusive devices.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, he terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

Various embodiments of the disclosed inventions are describedhereinafter with reference to the figures. It should be noted that thefigures are not drawn to scale and that elements of similar structuresor functions are represented by like reference numerals throughout thefigures. It should also be noted that the figures are only intended tofacilitate the description of the embodiments. They are not intended asan exhaustive description of the invention or as a limitation on thescope of the invention, which is defined only by the appended claims andtheir equivalents. In addition, an illustrated embodiment of thedisclosed inventions needs not have all the aspects or advantages shown.An aspect or an advantage described in conjunction with a particularembodiment of the disclosed inventions is not necessarily limited tothat embodiment and can be practiced in any other embodiments even ifnot so illustrated.

FIG. 1 illustrates a known vaso-occlusive device delivery system 10. Inthe system 10 illustrated in FIG. 1 , the vaso-occlusive device is avaso-occlusive coil 300. The system 10 includes a number ofsubcomponents or sub-systems. These include a delivery catheter 100, apusher assembly 200, a vaso-occlusive coil 300, and a power supply 400.The delivery catheter 100 includes a proximal end 102, a distal end 104,and a lumen 106 extending between the proximal and distal ends 102, 104.The lumen 106 of the delivery catheter 100 is sized to accommodate axialmovement of the pusher assembly 200 and the vaso-occlusive coil 300.Further, the lumen 106 is sized for the passage of a guidewire (notshown) which may optionally be used to properly guide the deliverycatheter 100 to the appropriate delivery site.

The delivery catheter 100 may include a braided-shaft construction ofstainless steel flat wire that is encapsulated or surrounded by apolymer coating. By way of non-limiting example, HYDROLENE® is a polymercoating that may be used to cover the exterior portion of the deliverycatheter 100. Of course, the system 10 is not limited to a particularconstruction or type of delivery catheter 100 and other constructionsknown to those skilled in the art may be used for the delivery catheter100. The inner lumen 106 may be advantageously coated with a lubriciouscoating such as PTFE to reduce frictional forces between the deliverycatheter 100 and the respective pusher assembly 200 and vaso-occlusivecoil 300 being moved axially within the lumen 106. The delivery catheter100 may include one or more optional marker bands 108 formed from aradiopaque material that can be used to identify the location of thedelivery catheter 100 within the patient’s vasculature system usingimaging technology (e.g., fluoroscope imaging). The length of thedelivery catheter 100 may vary depending on the particular application,but generally is around 150 cm in length. Of course, other lengths ofthe delivery catheter 100 may be used with the system 10 describedherein.

The delivery catheter 100 may include a distal end 104 that is straightas illustrated in FIG. 1 . Alternatively, the distal end 104 may bepre-shaped into a specific geometry or orientation. For example, thedistal end 104 may be shaped into a “C” shape, an “S” shape, a “J”shape, a 45° bend, a 90° bend. The size of the lumen 106 may varydepending on the size of the respective pusher assembly 200 andvaso-occlusive coil 300, but generally the OD of the lumen 106 of thedelivery catheter 100 (I.D. of delivery catheter 100) is less than about0.02 inches. The delivery catheter 100 is known to those skilled in theart as a microcatheter. While not illustrated in FIG. 1 , the deliverycatheter 100 may be utilized with a separate guide catheter (not shown)that aids in guiding the delivery catheter 100 to the appropriatelocation within the patient’s vasculature.

As illustrated in FIGS. 1 and 3 , the system 10 includes a pusherassembly 200 configured for axial movement within the lumen 106 of thedelivery catheter 100. The pusher assembly 200 generally includes aproximal end 202 and a distal end 204. The pusher assembly 200 includesa pusher conduit 214, which has a proximal tubular portion 206 and adistal coil portion 208, and defines a pusher lumen 212 and a distalopening in communication with the pusher lumen 212.

FIG. 3 illustrates a detailed longitudinal cross-sectional view of thejunction 250 between the pusher assembly 200 and the vaso-occlusive coil300 according to one embodiment of the disclosed inventions. Similarelements of this embodiment are identified with the same referencenumbers as discussed above with respect to FIG. 1 . The pusher assembly200 includes a proximal end 202 and a distal end 204 and measuresbetween around 184 cm to around 186 cm in length. The proximal tubularportion 206 may be formed from, for example, a flexible stainless steelhypotube. The proximal tubular portion 206 may be formed from stainlesssteel hypotube having an OD of .01325 inches and inner diameter (ID) of.0075 inches. The length of the hypotube section may be between around140 cm to around 150 cm, although other lengths may also be used.

A distal coil portion 208 is joined in end-to-end fashion to the distalface of the proximal tubular portion 206. The joining may beaccomplished using a weld or other bond. The distal coil portion 208 mayhave a length of around 39 cm to around 41 cm in length. The distal coilportion 208 may comprise a coil of 0.0025 inches x 0.006 inches. Thefirst dimension generally refers to the OD of the coil wire that formsthe coil. The latter dimension generally refers to the internal mandrelused to wind the coil wire around to form the plurality of coil windsand is the nominal ID of the coil. One or more windings of the distalcoil portion 208 may be formed from a radiopaque material, formingmarker coils. For example, the distal coil portion 208 may include asegment of stainless steel coil (e.g., 3 cm in length), followed by asegment of platinum coil (which is radiopaque and also 3 mm in length),followed by a segment of stainless steel coil (e.g., 37 cm in length),and so on and so forth.

An outer sleeve 232 or jacket surrounds a portion of the proximaltubular portion 206 and a portion of the distal coil portion 208 of thepusher conduit 214. The outer sleeve 232 covers the interface or jointformed between the proximal tubular portion 206 and the distal coilportion 208. The outer sleeve 232 may have a length of around 50 cm toaround 54 cm. The outer sleeve 232 may be formed from a polyether blockamide plastic material (e.g., PEBAX 7233 lamination). The outer sleeve232 may include a lamination of PEBAX and HYDROLENE® that may be heatlaminated to the pusher assembly 200. The OD of the outer sleeve 232 maybe less than 0.02 inches and advantageously less than 0.015 inches. Inthe embodiment depicted in FIG. 3 , the pusher conduit 214 forms anegative (i.e., return) conductor 222 (described below). Accordingly,the outer sleeve 232 is removed from the very distal end of the pusherconduit 214, during manufacturing, to form an exposed negativeelectrical contact 224. In other embodiments where the negativeconductor 222 is a separate wire running through the pusher conduit 224,the outer sleeve 232 may cover the entire pusher conduit 214, and thenegative electrical contact 224 may be a ring electrode disposed aroundthe proximal tubular portion 206 of the pusher conduit 214.

As shown in FIG. 3 , the system 10 also includes a proximal seal 230attached to the interior surface of the distal coil portion 208 of thepusher conduit 214 in the pusher lumen 212. The proximal seal 230 may beformed of an adhesive. A tubular member 226 is disposed in the proximalseal 230 and defines a tube lumen 228. A positive conductor 220 is awire that runs between the proximal and distal ends 202, 204 of thepusher assembly 200 in the pusher lumen 212 and into the tube lumen 228.The positive conductor 220 extends through the proximal seal 230 whilethe proximal seal 230 maintains a substantially fluid tight seal betweenregions proximal and distal of the proximal seal 230.

The positive conductor 220 may be formed from an electrically conductivematerial, such as copper wire coated with polyimide, with an OD ofaround 0.00175 inches. The proximal end of the positive conductor 220 iselectrically connected to a positive electrical contact 216. Asmentioned above, the pusher conduit 214 forms a negative conductor 222,and a portion of the pusher conduit 214 at the proximal end 202 forms anegative electrical contact 224. As shown in FIG. 1 , positive andnegative electrical contacts 216, 224 are located at the proximal end ofthe pusher assembly 200. The positive electrical contact 216 may beformed from a metallic solder (e.g., gold). Both the positive andnegative electrical contacts 216, 224 may be configured to interfacewith corresponding electrical contacts (not shown) in the power supply400 (described below). The positive conductors 220 may be coated with aninsulative coating such as polyimide except where it connects to thepositive electrical contact 216.

A sacrificial link 234 electrically connects the positive and negativeconductors 220, 222, and forms a circuit therewith. The sacrificial link234 is an elongate body having proximal and distal ends 236, 238. Thesacrificial link may be a strand/filament, a tube, or a ribbon. Thesacrificial link 234 is partially disposed in the tube lumen 228. Thesacrificial link 234 is made from an electrically conductive materialsuch as titanium, titanium alloy, nitinol, magnesium, magnesium alloy,various electrically conductive polymers, and combinations thereof.Electrically conductive polymers include polyacetylene, polypyrrole,polyaniline, poly(p-phenylene vinylene), poly(thiophene),poly(3,4-ethylenedioxythiophene), poly(p-phenylene sulfide), and variouspowder-filled or fiber-filled composite polymers., such as carbon filledpolymers. Powder-filled composite polymers include graphite-filledpolyolefins, graphite-filled polyesters, graphite-filled epoxies,graphite-filled silicones, silver-loaded epoxies, and silver-loadedsilicones. Fiber-filled composite polymers include carbon fibers,stainless steel fibers, nickel fibers, or aluminum fibers dispersed inpolyolefins, polyesters, epoxies, or silicones

When a current is applied through the sacrificial link 234, resistanceto current flows through the sacrificial link 234 generates heat thatthermally disintegrates (i.e., decomposes) the sacrificial link 234,breaking the electrical circuit. Resistance of the sacrificial link 234is much higher than that of the positive conductor 220 and the conduit208. The disparity in resistance focuses heat generation focus at thesacrificial link 234. While previously known heat actuated detachmentsystems utilize separate heating elements to melt attachment members,the system 10 depicted in FIG. 3 uses a conductive and resistivesacrificial link 234 to generate heat to thermally disintegrate itself.The distal coil portion 208 of the pusher assembly does not generateheat that affects the sacrificial link 234, because to current appliedthrough the circuit is relatively low.

The sacrificial link 234 also mechanically connects the vaso-occlusivecoil 300 to the pusher assembly 200. The vaso-occlusive coil 300includes a proximal end 302, a distal end 304, and a lumen 306 extendingthere between. The vaso-occlusive coil 300 is made from a biocompatiblemetal such as platinum or a platinum alloy (e.g., platinum-tungstenalloy). The vaso-occlusive coil 300 includes a plurality of coilwindings 308. The coil windings 308 are generally helical about acentral axis disposed along the lumen 306 of the vaso-occlusive coil300. The vaso-occlusive coil 300 may have a closed pitch configurationas illustrated in FIGS. 1 and 3 . A tether (not shown), such as asuture, may extend from the proximal end 302 through the lumen 306 tothe distal end 304 where it is connected to the distal end 304 of thevaso-occlusive coil 300.

The vaso-occlusive coil 300 generally includes a straight configuration(as illustrated in FIG. 1 ) when the vaso-occlusive coil 300 is loadedwithin the delivery catheter 100. Upon release, the vaso-occlusive coil300 generally takes a secondary shape which may includethree-dimensional helical configurations. FIG. 2 illustrates oneexemplary configuration of a vaso-occlusive coil 300 in a natural state.In the natural state, the vaso-occlusive coil 300 transforms from thestraight configuration illustrated in, for instance, FIG. 1 into asecondary shape. The secondary shaped may include both two and threedimensional shapes of a wide variety. FIG. 2 is just one example of asecondary shape of a vaso-occlusive coil 300 and other shapes andconfigurations are contemplated to fall within the scope of thedisclosed inventions. Also, the vaso-occlusive coil 300 may incorporatesynthetic fibers (not shown) over all or a portion of the vaso-occlusivecoil 300 as is known in the art. These fibers may be attached directlyto coil windings 308 or the fibers may be integrated into thevaso-occlusive coil 300 using a weave or braided configuration. Ofcourse, the system 10 described herein may be used with occlusive coils300 or other occlusive structures having a variety of configurations,and is not limited to occlusive coils 300 having a certain size orconfiguration.

The vaso-occlusive coil 300 depicted in FIG. 3 includes an adapter 310at its proximal end 302. The adapter 310 has proximal and distalportions 312, 314. The adapter 310 may be a flattened body defining anopening 316 at the distal end thereof. The adapter 310 may be formedfrom a non-conductive material. The distal portion 314 of the adapter310 is permanently attached to an interior surface of the vaso-occlusivecoil 300 at the proximal end of the occlusive coil lumen 306. The distalportion 314 of the adapter 310 may be attached to the occlusive coilwith an adhesive.

The proximal portion 312 of the adapter 310 is detachably connected(i.e., releasably attached) to the pusher assembly 200 by thesacrificial link 234. The proximal end 236 of the sacrificial link 234is mechanically and electrically connected to the positive conductor220. The sacrificial link 234 also forms a loop 240 passing through theopening 316 in the adapter 310. The distal end 238 of the sacrificiallink 234 is mechanically and electrically connected to the negativeconductor 222, i.e. the pusher conduit 214. Interference between theloop 240 of the sacrificial link 234 and the opening 316 the adapter 310mechanically connects the vaso-occlusive device 300 to the pusherassembly 200.

As shown in FIG. 1 , the system 10 further includes a power supply 400for supplying direct current to the positive and negative conductors220, 222. Activation of the power supply 400 causes electrical currentto flow in a circuit including the positive and negative conductors 220,222 and the sacrificial link 234. The power supply 400 preferablyincludes an onboard energy source, such as batteries (e.g., a pair ofAAA batteries), along with drive circuitry 402. The drive circuitry 402may include one or more microcontrollers or processors configured tooutput a driving current. The power supply 400 illustrated in FIG. 1includes a receptacle 404 configured to receive and mate with theproximal end 202 of the delivery wire assembly 200. Upon insertion ofthe proximal end 202 into the receptacle 404, the positive, negativeelectrical contracts 216, 224 disposed on the delivery wire assembly 200electrically couple with corresponding contacts (not shown) located inthe power supply 400.

A visual indicator 406 (e.g., LED light) is used to indicate when theproximal end 202 of delivery wire assembly 200 has been properlyinserted into the power supply 400. Another visual indicator 420 isactivated if the onboard energy source needs to be recharged orreplaced. The power supply 400 includes an activation trigger or button408 that is depressed by the user to apply the electrical current to thesacrificial link 234 via the positive and negative conductors 220, 222.Once the activation trigger 408 has been activated, the driver circuitry402 automatically supplies current. The drive circuitry 402 typicallyoperates by applying a substantially constant current, e.g., around50-1,000 mA. Alternatively, the drive circuitry 402 can operate byapplying two different currents, e.g., 350 mA (relatively high current)and 100 mA (relatively low current) for different functions, asdescribed below. A visual indicator 412 may indicate when the powersupply 400 is supplying adequate current to the sacrificial link 234.

The power supply 400 may optionally include detection circuitry 416 thatis configured to detect when the vaso-occlusive coil 300 has detachedfrom the pusher assembly 200. The detection circuitry 416 may identifydetachment based upon a measured impedance value. Another visualindicator 414 may indicate when the occlusive coil 300 has detached fromthe pusher assembly 200. As an alternative to the visual indicator 414,an audible signal (e.g., beep) or even tactile signal (e.g., vibrationor buzzer) may be triggered upon detachment. The detection circuitry 416may be configured to disable the drive circuitry 402 upon sensingdetachment of the occlusive coil 300.

In use, the vaso-occlusive coil 300 is attached to the pusher assembly200 at junction 250. The attached vaso-occlusive coil 300 and pusherassembly 200 are threaded through the delivery catheter 100 to a targetlocation (e.g., an aneurysm) in the patient’s vasculature. Once thedistal end 304 of the vaso-occlusive coil 300 reaches the targetlocation, the vaso-occlusive coil 300 is pushed further distally untilit’s completely exits the distal end 104 of the delivery catheter 100.

In order to detach the vaso-occlusive coil 300 from the pusher assembly200, the power supply 400 is activated by depressing the trigger 408.The drive circuitry 402 in the power supply 400 applies a current to thepositive and negative conductors 220, 222 through the positive andnegative electrical contacts 216, 224. As the applied current travelsthrough the sacrificial link 234, the sacrificial link 234 generatesheat. The generated heat thermally disintegrates the sacrificial link234. After activation of the power supply 400, the vaso-occlusive coil300 is typically detached in less than 1.0 second.

Because most of the sacrificial link 234 is located in the pusher lumen212, the distal end of the pusher conduit 214 including the distal endof the outer sleeve 232 thermally insulates the sacrificial link 234from the environment external to the pusher assembly 200. Thisinsulation both protects tissue adjacent the pusher assembly 200 andincreases the heat applied to the sacrificial link 234.

The vaso-occlusive device delivery systems 10 depicted in FIGS. 4-7 aresimilar to the system 10 depicted in FIG. 3 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 3 . A feature common to the systems 10depicted in FIGS. 4 to 7 that is different from the system 10 depictedin FIG. 3 is that the negative conductor 222 is a wire that runs betweenthe proximal and distal ends 202, 204 of the pusher assembly 200 in thepusher lumen 212, like the positive conductor 220. The positive andnegative conductors 220, 222 both run through the proximal seal 230 andthe tubular member 226. As described above, in embodiments where boththe positive and negative conductors 220, 222 are wires running throughthe pusher lumen 212, the outer sleeve 232 may cover the entire pusherconduit 214, and the negative electrical contact 224 may be a ringelectrode disposed around the proximal tubular portion 206 of the pusherconduit 214 and electrically connected to a proximal end of the negativeconductor 222.

Another feature common to the systems 10 depicted in FIGS. 4 to 7 isthat the positive and negative conductors 220, 222 are connected toeach, other distal of the tubular member, by the sacrificial link 234.In the system 10 depicted in FIG. 4 , the sacrificial link 234 is anelongate member 234 connecting the respective distal terminal ends ofthe positive and negative conductors 220, 222. One of the conductors, inthis case the negative conductor 222, forms a loop 240 through theopening 316 in the adapter 310, thereby mechanically connecting thevaso-occlusive coil 300 to the pusher assembly 200. When current isapplied through the sacrificial link 234, sacrificial link 234 isthermally disintegrated by resistive heating, thereby releasing thevaso-occlusive coil 300 from the pusher assembly 200.

In the system 10 depicted in FIG. 5 , the sacrificial link 234 is in theform of a small tube 234. The respective distal ends of the positive andnegative conductors 220, 222 extend into the small tube 234 throughopposite openings, and are attached to the sacrificial link 234 therein.Otherwise, the system 10 depicted in FIG. 5 is identical to the system10 depicted in FIG. 4 .

As in the system 10 depicted in FIG. 4 , the sacrificial link 234depicted in FIG. 6 is an elongate member 234 connecting the respectivedistal terminal ends of the positive and negative conductors 220, 222.In the embodiment depicted in FIG. 6 , however, the elongate member 234forms a loop 240 through the opening 316 in the adapter 310, therebymechanically connecting the vaso-occlusive coil 300 to the pusherassembly 200. Otherwise, the system 10 depicted in FIG. 6 is identicalto the system 10 depicted in FIG. 4 .

The system 10 depicted in FIG. 7 is similar to the system 10 depicted inFIG. 6 . However the loop 240 formed by the elongate member/sacrificiallink 234 does not pass through the opening 316 in the adapter 310.Instead a locking ring 242 mechanically connects the elongate memberloop 240 to the opening 316 in the adapter 310.

The vaso-occlusive device delivery systems 10 depicted in FIGS. 8-14 aresimilar to the system 10 depicted in FIG. 3 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 3 . The systems 10 depicted in FIGS. 8, 9,and 11-14 do not have separate insulating tubular members. Instead thesacrificial links 234 are directly connected to the respective pusherconduit 214 in the pusher lumen 212. The arrows in the positiveconductor 220, sacrificial link 234, and the pusher conduit 214illustrate the current flow. The sacrificial links 234 depicted in FIGS.8 to 14 are cylindrical bodies with an OD approximately equal to the IDof the pusher conduit 214. Therefore, when the sacrificial links 234 areinserted into the respective pusher lumens 212, the outer surface ofsacrificial links 234 are in direct contact with an inner surface of therespective pusher conduits 214. The proximal ends 236 of the sacrificiallinks 234 are also attached to the respective proximal seals 230. Thedistal ends 238 of sacrificial links 234 are attached to distal seals318 disposed in the lumens 306 of the respective vaso-occlusive coils300, thereby connecting the vaso-occlusive coils 300 with the respectivepusher assemblies 200. The distal seals 318 can be formed fromadhesives.

In the system depicted in FIG. 8 , sacrificial link 234 is a conductivetube 234 having a conductive tube lumen 244. The distal end of thepositive conductor 220 is disposed in the conductive tube lumen 244. Theentire portion of the positive connector 220 disposed in the conduct oftube lumen 244 is bare wire in electrical contact with the conductivetube 234. When current is applied through the sacrificial link 234,sacrificial link 234 is thermally disintegrated by resistive heating,thereby releasing the vaso-occlusive coil 300 from the pusher assembly200. Although the outer sleeve 232 depicted in FIG. 8 does not extend tothe distal terminal end of the pusher assembly 200, in other embodimentsthe outer sleeve 232 can extend to the distal terminal end and distallybeyond.

The system 10 depicted in FIG. 9 is similar to the system 10 depicted inFIG. 8 , except that the outer sleeve 232 extends further distally inthe system 10 depicted in FIG. 9 to cover and further insulate theconductive tube/sacrificial link 234.

The system 10 depicted in FIG. 10 is similar to the system 10 depictedin FIG. 9 , except that an insulating tubular member 226 is disposedaround the proximal end 236 of the conductive tube/sacrificial link 234.The tubular member 226 insulates the proximal end 236 of the conductivetube 234 from the negative conductor 222. However the terminal mostwinding 246 of the negative conductor 222 (pusher conduit 214) extendsdistally beyond the tubular member 226, thereby electrically connectingthe positive and negative conductors 220, 222 through a smaller area.Further, only the distal most portion 248 of the positive conductor 220is exposed, thereby further reducing the area of electrical contactbetween the positive and negative conductors 220, 222, and increasingthe resistivity of the sacrificial link 234 and the heat generatedtherein.

The vaso-occlusive device delivery systems 10 depicted in FIGS. 11-14are similar to the systems 10 depicted in FIGS. 8-10 . Similar elementsof this embodiment are identified with the same reference numbers asdiscussed above with respect to FIGS. 8-10 . The respective sacrificiallinks 234 depicted in FIGS. 11-14 are elongate bodies 234 defining openproximal ends 236, close distal ends 238, and conductive bore lumens244. The elongate bodies 234 are connected to respective proximal anddistal seals 230, 318, thereby connecting the vaso-occlusive coils 300from the pusher assemblies 200. The elongate bodies 234 can be injectionmolded around their respective positive conductors 220.

In the system 10 depicted in FIG. 11 , the positive conductor 220extends into the conductive bore lumen 244 and is electrically connectedto the elongate body 234 therein. The system 10 depicted in FIG. 12 issimilar to the system 10 depicted in FIG. 11 , except that the distalend of the positive conductor 220 has a protrusion 252 extendingobliquely along a longitudinal axis of the first conductor and into theelongate body 234. The protrusion 252 forms a hook securing the positiveconductor 220 in the elongate body 234, and strengthening the mechanicalconnection therebetween.

The system 10 depicted in FIG. 13 is similar to the system 10 depictedin FIG. 12 . Instead of an oblique protrusion, the distal end of thepositive connector 220 includes a radially enlarged portion 254 but alsostrengthens the mechanical connection between the positive conductor 220and the conductor bore 234. The radially enlarged portion 254 alsoconcentrates current density in the distal end of the positive connector220.

System depicted in FIG. 14 this similar to the system 10 depicted inFIG. 11 , except that the proximal end 236 of the elongate body 234extends completely through the proximal seal 230. This designfacilitates separation of vaso-occlusive coil 300 from the pusherassembly 200.

The vaso-occlusive device delivery system 10 depicted in FIG. 15 issimilar to the system 10 depicted in FIG. 3 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 3 . The proximal and distal ends 236, 238 ofthe sacrificial link 234 form proximal and distal spherical enlargements236, 238, respectively, forming a “dog-bone” shape. The proximalspherical enlargement 236 is disposed in and connected to the proximalseal 230, which is itself connected to the distal end of the pusherconduit 214. The proximal seal 230 may be made from a non-conductivepolymer, and includes distally extending portion 256 that thermallyinsulates the sacrificial link 234.

The distal spherical enlargement 238 is disposed in an opening 316 inthe adapter 310 and connected to the adapter 310, which is itselfconnected to the proximal end 302 of the vaso-occlusive coil 300. Theproximal and distal spherical enlargements 236, 238 strengthen themechanical connections between the sacrificial link 234 and the proximalseal 230 and the adapter 310. Further, the vaso-occlusive coil 300depicted FIG. 15 also includes a stretch-resisting member 320 attachedto the distal end 304 of vaso-occlusive coil 300. The proximal end ofthe stretch-resisting member 320 forms a loop 322 passing through asecond opening 316 in the adapter 310, thereby attaching thestretch-resisting member 320 to the adapter 310.

The vaso-occlusive device delivery system 10 depicted in FIG. 16 issimilar to the system 10 depicted in FIG. 15 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 15 . The sacrificial link 234 depicted inFIG. 16 is an elongate body forming a loop 240. The sacrificial link 234is connected to a polymer proximal seal 230 similar to the one depictedin FIG. 15 . The adapter 310 includes a ring 324 disposed in the distalseal 318 and the tether 326 extending proximally of the distal seals318. The tether is threaded through the loop 240 formed by thesacrificial link 234. The stretch-resisting member 320 is threadedthrough the ring 324 in the adapter 310, thereby connecting thevaso-occlusive coil 300 to the pusher assembly 200. The vaso-occlusivecoil 300 also includes a cylindrical member 328 disposed around thetether 326.

The vaso-occlusive device delivery system 10 depicted in FIG. 17 issimilar to the system 10 depicted in FIG. 16 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 16 . There are two differences between thesystems 10 depicted in FIGS. 16 and 17 . First, the proximal seal 230depicted in FIG. 17 does not have a distally extending portion like theone depicted in FIG. 16 . Instead, the outer sleeve 232 of the pusherassembly 200 extends distally of the pusher conduit 214, thermallyinsulating the sacrificial link 234.

The vaso-occlusive device delivery system 10 depicted in FIG. 18 issimilar to the system 10 depicted in FIG. 17 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 17 . The system 10 depicted in FIG. 18 is notinclude an adapter like the one depicted in FIG. 17 . Instead, thestretch-resisting member 320 extends through the distal seal 318 and thecylindrical member 328 to form a loop 322 through the loop 240 formed bythe sacrificial link 234.

FIGS. 19 to 23 depict a composite sacrificial link 234 for use with anyof the above-described embodiments. The sacrificial link 234 includes anelectrically conductive member 258 partially disposed in an electricallyinsulating member 260, leaving an exposed portion 262 of theelectrically conductive member 258. Sacrificial link 234 also definesgrooves 264 for connecting to positive and negative conductors (see FIG.23 ), and an opening 266 for connecting to the vaso-occlusive coil (seeFIG. 23 ). In FIG. 23 , the proximal end 302 of the vaso-occlusive coil300 includes an open winding 330 loop through the opening 266 in thesacrificial link 234. Positive and negative conductors can beelectrically connected to the electrically conductive member 258 by aconductive adhesive or welding 268. When a current is applied throughthe sacrificial link 234, resistive heating thermally disintegrates theexposed portion 262 of the electrically conductive member 258, therebyreleasing the vaso-occlusive coil 300 from the pusher assembly 200.

The electrically conductive member 258 can be made of a conductivepolymer, such as any those described above. The electrically insulatingmember can be made from any non-conductive polymer. Rigid non-conductivepolymers include polycarbonate and polystyrene. Soft non-conductivepolymers include silicone and polyurethane. The sacrificial link 234 canbe made by either co-molding the conductive and non-conductive polymers,or over-molding the nonconductive polymer on top of the conductivepolymer.

The sacrificial link 234 depicted in FIG. 21 includes a notch 270 in theelectrically conductive member 258. As shown in FIG. 21 , thecross-sectional area of the electrically conductive member 258 is at aminimum at the notch 270. The decreased cross-sectional area increasesresistance, thereby increasing heat generated at the notch 270. Thesacrificial link 234 depicted in FIG. 22 includes a small gap 272 in theelectrically conductive member 258. When current is applied through thesacrificial link 234, the current will arc through the 272, generating alarge amount of heat and sparks to thermally disintegrate the exposedportion 262 of the electrically conductive member 258.

The vaso-occlusive device delivery system 10 depicted in FIG. 24 issimilar to the system 10 depicted in FIG. 15 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 15 . Like the sacrificial link 234 depictedin FIG. 15 , the sacrificial link 234 depicted in FIG. 24 has proximaland distal spherical enlargements 236, 238 in its proximal and distalends 236, 238, respectively, forming a “dog-bone” shape. However, theproximal spherical enlargement 236 of the sacrificial link 234 extendsproximally of the proximal seal 230, creating a mechanical interferencewith the proximal seal 230 preventing distal movement of the sacrificiallink 234. Further, the distal spherical enlargement 238 to sacrificiallink 234 extends distally of the distal seal 318, creating a mechanicalinterference with the distal seal 318 preventing proximal movement ofthe sacrificial link 234. Sacrificial link 234 also includes an exposedportion 262 between the proximal and distal seals 230, 318. Moreover,the stretch-resisting member 320 forms a loop 322 around the distalspherical enlargement 238, connecting the stretch-resisting member 320to the sacrificial link 234. When current is applied through thesacrificial link 234, heat is generated at the exposed portion 262,thermally disintegrating the exposed portion 262 and releasing thevaso-occlusive coil 300 from the pusher assembly 200.

The vaso-occlusive device delivery system 10 depicted in FIG. 25 issimilar to the system 10 depicted in FIG. 24 . Similar elements of thisembodiment are identified with the same reference numbers as discussedabove with respect to FIG. 24 . The proximal and distal seals 230, 318depicted in FIG. 25 each have a flat profile. The sacrificial link 234is disposed in the proximal seal 230, except for an exposed portion 262,which is connected to the proximal end of the distal seal 318. Theproximal and distal seals 230, 318 each define respective pluralities offingers 274, 276. The distal terminal end of the distal coil portion 208of the pusher conduit 214 and the proximal terminal end of thevaso-occlusive coil 300 each include open windings 246, 330. The fingers274 defined by the proximal seal 230 are interlaced between adjacentopen windings 246 of the distal terminal end of the distal coil portion208, mechanically connecting the proximal seal 230, and the sacrificiallink 234 contained therein, to the pusher conduit 214. The fingers 276defined by the distal seal 318 are interlaced between adjacent openwindings 330 of the proximal terminal end of the vaso-occlusive coil300, mechanically connecting the distal seal 318, and the sacrificiallink 234 attached thereto, to the vaso-occlusive coil 300. When currentis applied through the sacrificial link 234, heat is generated at theexposed portion 262, thermally disintegrating the exposed portion 262and releasing the vaso-occlusive coil 300 from the pusher assembly 200.

FIG. 26 illustrates a schematic view of the junction 250 between thepusher assembly 200 and the vaso-occlusive coil 300 according to oneembodiment of the disclosed inventions. The system 10 depicted in FIG.26 is similar to the system 10 depicted in FIG. 18 . Similar elements ofthis embodiment are identified with the same reference numbers asdiscussed above with respect to FIG. 18 . The system 10 includespositive and negative conductors 220, 222 and a sacrificial link 234connected thereto. The positive and negative conductors 220, 222 aredisposed on the proximal side of the proximal seal 230 in thesacrificial link 234 is disposed on the distal side of the proximal seal230. First and second load bearing connectors 278, 280 connected distalends of the positive and negative conductors 220, 222 two opposite sidesof the sacrificial link 234, respectively. While the first and secondload bearing connectors 278, 280 form rings for attachment of thepositive and negative conductors 220, 222 and the sacrificial link 234,the load bearing connectors 278, 280 and the positive and negativeconductors 220, 222 and the sacrificial link 234 may be tied to eachother. Sacrificial link 234 is made of the material such as nitinol(other materials described above) that thermally disintegrates uponapplication of a relatively high current, for example 350 mA.

A stretch-resisting member 320 passes proximally through the distal seal318 and forms a loop 322 around the sacrificial link 234, therebyconnecting the vaso-occlusive coils 300 to the pusher assembly 200. Thestretch-resisting member 320 is formed from a low melting point polymer.

In use the system 10 depicted in FIG. 26 has two modes of operation todetach the vaso-occlusive device 300 from the pusher assembly 200. Inthe “melting mode,” the relatively low current, for example 100 mA, isapplied through the sacrificial link 234. This generates small amount ofheat, which is not sufficient to generate a temperature that willdisintegrate the sacrificial link 234. However, this heat is sufficientto generate a temperature that will melt the stretch-resisting member320 looping through an in contact with the sacrificial link 234,detaching the vaso-occlusive device 300 the pusher assembly 200. In the“disintegrating mode,” a relatively high current, for example 350 mA, isapplied through the sacrificial link 234, the relatively high currentgenerates a temperature that thermally disintegrates to sacrificial link234, detaching the vaso-occlusive device 300 from the pusher assembly200. The power supply 400 can be controllable to selectively deliver therelatively low current or the relatively high current to the sacrificiallink 234.

The systems 10 depicted in FIG. 27 is similar to the system 10 depictedin FIG. 26 . Similar elements of this embodiment are identified with thesame reference numbers as discussed above with respect to FIG. 26 . Thesystem depicted in FIG. 27 includes an alternative positive conductor282, which has a higher resistivity than the positive conductor 220. Inthis case, the alternative positive conductor 282 has a higherresistivity because it is length of nitinol wire, thereby increasing thetotal length of nitinol wire in the circuit. The alternative positiveconductor 282 is also connected to the sacrificial link 234 such thatthe alternative positive and negative conductors 282, 222 and thesacrificial link 234 form circuit.

When a relatively high current, is applied through the alternativepositive and negative conductors 282, 222 and the sacrificial link 234,the heat generated by the resistance of sacrificial link 234 does notraise the temperature of the sacrificial link 234 sufficiently tothermally disintegrate the sacrificial link 234. However, applying arelatively high current through the alternative positive and negativeconductors 282, 222 and the sacrificial link 234 does raise thetemperature of sacrificial link 234 sufficiently to melt thestretch-resisting member 320 in contact therewith. Accordingly, thepower supply 400 can select between the “melting mode” and“disintegrating mode” by flowing current through either the positive oralternative positive conductors 220, 282, instead of varying the amountof current flowed through the system 10.

The systems 10 depicted in FIG. 28 is similar to the system 10 depictedin FIG. 26 . Similar elements of this embodiment are identified with thesame reference numbers as discussed above with respect to FIG. 26 . Inthe system 10 depicted in FIG. 28 , the positive and negative conductors220, 222 extend distally through the proximal seal 230 and connectdirectly to the sacrificial link 234. In this case, the positive andnegative conductors 220, 222 are wrapped around respective opposite endsof the sacrificial link 234 and soldered thereto, mechanically andelectrically connecting the conductors 220, 22 to the sacrificial link234 without load bearing connectors.

Although particular embodiments of the disclosed inventions have beenshown and described herein, it will be understood by those skilled inthe art that they are not intended to limit the present inventions, andit will be obvious to those skilled in the art that various changes andmodifications may be made (e.g., the dimensions of various parts)without departing from the scope of the disclosed inventions, which isto be defined only by the following claims and their equivalents. Thespecification and drawings are, accordingly, to be regarded in anillustrative rather than restrictive sense. The various embodiments ofthe disclosed inventions shown and described herein are intended tocover alternatives, modifications, and equivalents of the disclosedinventions, which may be included within the scope of the appendedclaims.

What is claimed is:
 1. A vaso-occlusive device delivery assembly,comprising: a pusher assembly, the pusher assembly comprising a proximalend, a distal end, first and second conductors extending between theproximal and distal ends, a thermally-degradable conductive sacrificiallink disposed at the distal end and electrically coupled between therespective first and second conductors, such that the first conductor,the sacrificial link, and the second conductor form an electricalcircuit, and an outer sleeve coupled to and completely covering thesacrificial link and configured to thermally insulate the sacrificiallink from an environment external to the pusher assembly; and avaso-occlusive device secured to the pusher assembly by the sacrificiallink, wherein the sacrificial link is configured to generate heat thatthermally disintegrates the sacrificial link when a disintegrationcurrent is applied through the sacrificial link, thereby releasing thevaso-occlusive device from the pusher assembly.
 2. The assembly of claim1, wherein the pusher assembly further comprises a pusher conduit havinga lumen, and a proximal seal affixed within the lumen of the pusherconduit.
 3. The assembly of claim 2, wherein the pusher assembly furthercomprises a distal seal affixed within a lumen of the vaso-occlusivedevice.
 4. The assembly of claim 2, wherein the sacrificial linkcomprises a loop connected to the proximal seal.
 5. The assembly ofclaim 1, wherein the sacrificial link is a composite sacrificial linkthat includes an electrically conductive member and an electricallyinsulating member partially disposed in the electrically conductivemember, leaving an exposed portion of the electrically conductivemember.
 6. The assembly of claim 5, wherein the composite sacrificiallink defines an opening to which the vaso-occlusive device is connected.7. The assembly of claim 5, wherein the electrically conductive memberis composed of conductive polymer, and the electrically insulatingmember is composed of a non-conductive polymer.
 8. The assembly of claim5, wherein the electrically conductive member comprises one of a notchand a small gap.
 9. A vaso-occlusive device delivery assembly,comprising: a pusher assembly, the pusher assembly comprising a proximalend, a distal end, first and second conductors extending between theproximal and distal ends, a thermally-degradable composite sacrificiallink disposed at the distal end and electrically coupled between therespective first and second conductors, the composite sacrificial linkincluding an electrically conductive member and an electricallyinsulating member partially disposed in the electrically conductivemember, leaving an exposed portion of the electrically conductivemember, such that the first conductor, the electrically conductivemember, and the second conductor, respectively, form an electricalcircuit, and an outer sleeve coupled to and completely covering thesacrificial link and configured to thermally insulate the sacrificiallink from an environment external to the pusher assembly; and avaso-occlusive device secured to the pusher assembly by the sacrificiallink, wherein the composite sacrificial link is configured to generateheat that thermally disintegrates the sacrificial link when adisintegration current is applied through the sacrificial link, therebyreleasing the vaso-occlusive device from the pusher assembly, andwherein the pusher assembly further comprises a pusher conduit having alumen, a proximal seal affixed within the lumen of the pusher conduit.10. The assembly of claim 9, wherein the pusher assembly furthercomprises a distal seal affixed within a lumen of the vaso-occlusivedevice.
 11. The assembly of claim 9, wherein the sacrificial linkcomprises a loop connected to the proximal seal.
 12. The assembly ofclaim 9, wherein the composite sacrificial link defines an opening towhich the vaso-occlusive device is connected.
 13. The assembly of claim9, wherein the electrically conductive member is composed of conductivepolymer, and the electrically insulating member is composed of anon-conductive polymer.
 14. The assembly of claim 9, wherein theelectrically conductive member comprises one of a notch and a small gap.15. A vaso-occlusive device delivery assembly, comprising: a pusherassembly, the pusher assembly comprising a proximal end, a distal end,first and second conductors extending between the proximal and distalends, a thermally-degradable composite sacrificial link disposed at thedistal end and electrically coupled between the respective first andsecond conductors, the composite sacrificial link including anelectrically conductive member and an electrically insulating memberpartially disposed in the electrically conductive member, leaving anexposed portion of the electrically conductive member, such that thefirst conductor, the electrically conductive member, and the secondconductor, respectively, form an electrical circuit, and an outer sleevecoupled to and completely covering the sacrificial link and configuredto thermally insulate the sacrificial link from an environment externalto the pusher assembly; and a vaso-occlusive device secured to thepusher assembly by the sacrificial link, wherein the compositesacrificial link is configured to generate heat that thermallydisintegrates the sacrificial link when a disintegration current isapplied through the sacrificial link, thereby releasing thevaso-occlusive device from the pusher assembly, wherein the pusherassembly further comprises a pusher conduit having a lumen, a proximalseal affixed within the lumen of the pusher conduit, and a distal sealaffixed within a lumen of the vaso-occlusive device, and wherein thesacrificial link comprises a loop connected to the proximal seal. 16.The assembly of claim 15, wherein the electrically conductive member iscomposed of conductive polymer, and the electrically insulating memberis composed of a non-conductive polymer.
 17. The assembly of claim 16,wherein the electrically conductive member comprises one of a notch anda small gap.